1. Technical Field
The present invention relates to a structure of each of an electronic device, a resonator and an oscillator having a functional structural body such as MEMS (micro electro mechanical systems) disposed in a cavity part configured on a substrate and to a method for manufacturing an electronic device.
2. Related Art
In general, an electronic device having a functional structural body such as MEMS disposed in a cavity part is known. MEMS, for example, micro oscillators, micro sensors and micro actuators, are accommodated in a cavity part in a movable state because a micro structural body is required to be disposed in a state such that oscillation, deformation or other movement is possible (see, for example, JP-A-2005-297180 and JP-A-2005-123561).
Now, as disclosed in JP-A-2005-297180, a method in which after forming a micro functional structural body on a surface of a one-sided substrate, the one-sided substrate is joined with the other-sided substrate in a vacuum chamber via an O-ring, and thereafter, a sealer is filled in the outside of the O-ring is known as a method for forming the foregoing cavity.
Also, as disclosed in JP-A-2005-123561, a method in which after forming an MEMS structural body on a substrate and forming a sacrifice layer thereon, a first sealing member having a through-hole is formed, the sacrifice layer is removed through the through-hole of this first sealing member to release a movable part of the MEMS structural body, and finally, the through-hole of the first sealing member is covered by a second sealing member to achieve closing is known as other method.
Also, a method similar to those in JP-A-2005-297180 and JP-A-2005-123561, in which in a structure having a complementary metal oxide semiconductor (CMOS) and an MEMS structural body monolithically configured therein, a cavity part is formed at the same time by employing a wiring forming technology of MOSFET, is described (see, for example, JP-A-2006-263902).
However, the method of sticking two substrates as described in JP-A-2005-297180 involves a problem that since a substrate for exclusive use is necessary, material costs increase, and even if it is intended to form a micro mechanical device by employing a general semiconductor manufacturing technology, since a special process for sticking the substrates to each other is necessary, advantages to be brought by employing the semiconductor manufacturing technology are reduced, and the manufacturing costs increase.
Also, the method of using a first sealing member having a through-hole and a second sealing member for closing the through-hole as disclosed in JP-A-2005-123561 involves a problem that since the release process of the MEMS structural body is carried out through the through-hole of the first sealing member, it takes a long period of time for achieving etching so that the first sealing member must be formed of a raw material capable of thoroughly withstanding the etching of the release process, and as a result, the first sealing member cannot be formed in a common process to the semiconductor manufacturing process, leading to an increase of the manufacturing costs.
The structure having a complementary metal oxide semiconductor (CMOS) and an MEMS structural body monolithically configured therein also involves the same problems as those described above.